package com.anyuan.wx.util;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;

public class SignUtil {
	
	private static String token = "weixinCourse";
	
	public static boolean checkSigature(String signature,String timestamp,String nonce)
	{
		String[] paramArr = new String[] {token,timestamp,nonce};
		Arrays.sort(paramArr);
		String content = paramArr[0].concat(paramArr[1]).concat(paramArr[2]);
		
		String ciphertext = null;
		try{
			MessageDigest md = MessageDigest.getInstance("SHA-1");
			byte[] digest = md.digest(content.toString().getBytes());
			ciphertext = byteToStr(digest);
		}catch(NoSuchAlgorithmException e) {
			e.printStackTrace();
		}
		
		return ciphertext != null? ciphertext.equals(signature.toUpperCase()):false;
	}
	
	private static String byteToStr(byte[] bytearray){
		String strDigest = "";
		for(int i = 0;i<bytearray.length;i++){
			strDigest += byteToHexStr(bytearray[i]);
		}
		return strDigest;
				
	}
	
	private static String byteToHexStr(byte ib){
		char[] Digit = {'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};
		char[] ob = new char[2];
		ob[0] = Digit[(ib >>> 4) & 0X0F];
		ob[1] = Digit[ib & 0X0F];
		
		String s = new String(ob);
	    return s;
	
}
	
}